fix: create fallback symbols for mappings without BuildIDs (#4527)

* fix: create fallback symbols for mappings without BuildIDs

Author: marcsanmi

pkg/symbolizer/symbolizer.go

@@ -99,12 +99,7 @@ func (s *Symbolizer) SymbolizePprof(ctx context.Context, profile *googlev1.Profi
 			return fmt.Errorf("extract build ID: %w", err)
 		}
 
-		if buildID == "" {
-			continue
-		}
-
 		req := s.createSymbolizationRequest(binaryName, buildID, locations)
-
 		s.symbolize(ctx, &req)
 
 		for i, loc := range locations {
@@ -247,33 +242,39 @@ func (s *Symbolizer) updateAllSymbolsInProfile(
 }
 
 func (s *Symbolizer) symbolize(ctx context.Context, req *request) {
-	var table *lidia.Table
-	var err error
+	if req.buildID == "" {
+		s.metrics.debugSymbolResolutionErrors.WithLabelValues("empty_build_id").Inc()
+		s.setFallbackSymbols(req)
+		return
+	}
 
 	lidiaBytes, err := s.getLidiaBytes(ctx, req.buildID)
 	if err != nil {
 		level.Warn(s.logger).Log("msg", "Failed to get debug info", "buildID", req.buildID, "err", err)
-		for _, loc := range req.locations {
-			loc.lines = s.createNotFoundSymbols(req.binaryName, loc)
-		}
+		s.setFallbackSymbols(req)
 		return
 	}
 
 	lidiaReader := NewReaderAtCloser(lidiaBytes)
-	table, err = lidia.OpenReader(lidiaReader, lidia.WithCRC())
+	table, err := lidia.OpenReader(lidiaReader, lidia.WithCRC())
 	if err != nil {
 		s.metrics.debugSymbolResolutionErrors.WithLabelValues("lidia_error").Inc()
 		level.Warn(s.logger).Log("msg", "Failed to open Lidia file", "err", err)
-		for _, loc := range req.locations {
-			loc.lines = s.createNotFoundSymbols(req.binaryName, loc)
-		}
+		s.setFallbackSymbols(req)
 		return
 	}
 	defer table.Close()
 
 	s.symbolizeWithTable(table, req)
 }
 
+// setFallbackSymbols sets fallback symbols for all locations in the request
+func (s *Symbolizer) setFallbackSymbols(req *request) {
+	for _, loc := range req.locations {
+		loc.lines = s.createFallbackSymbol(req.binaryName, loc)
+	}
+}
+
 func (s *Symbolizer) symbolizeWithTable(table *lidia.Table, req *request) {
 	var framesBuf []lidia.SourceInfoFrame
 
@@ -285,12 +286,12 @@ func (s *Symbolizer) symbolizeWithTable(table *lidia.Table, req *request) {
 	for _, loc := range req.locations {
 		frames, err := table.Lookup(framesBuf, loc.address)
 		if err != nil {
-			loc.lines = s.createNotFoundSymbols(req.binaryName, loc)
+			loc.lines = s.createFallbackSymbol(req.binaryName, loc)
 			continue
 		}
 
 		if len(frames) == 0 {
-			loc.lines = s.createNotFoundSymbols(req.binaryName, loc)
+			loc.lines = s.createFallbackSymbol(req.binaryName, loc)
 			continue
 		}
 
@@ -406,7 +407,7 @@ func (s *Symbolizer) processELFData(data []byte) (lidiaData []byte, err error) {
 	return memBuffer.Bytes(), nil
 }
 
-func (s *Symbolizer) createNotFoundSymbols(binaryName string, loc *location) []lidia.SourceInfoFrame {
+func (s *Symbolizer) createFallbackSymbol(binaryName string, loc *location) []lidia.SourceInfoFrame {
 	prefix := "unknown"
 	if binaryName != "" {
 		prefix = binaryName

pkg/symbolizer/symbolizer_test.go

@@ -96,16 +96,31 @@ func TestSymbolizePprof(t *testing.T) {
 			},
 		},
 		{
-			name: "empty build ID",
+			name: "empty build ID creates fallback symbols",
 			profile: &googlev1.Profile{
 				Mapping: []*googlev1.Mapping{{
-					BuildId: 1,
+					Id:       1,
+					Filename: 2,
+					BuildId:  1,
 				}},
-				StringTable: []string{"", ""},
+				Location: []*googlev1.Location{
+					{Id: 1, MappingId: 1, Address: 0xa4c},
+					{Id: 2, MappingId: 1, Address: 0x9f0},
+				},
+				StringTable: []string{"", "", "linux-vdso.1.so"},
 			},
 			setupMock: func(mockClient *mocksymbolizer.MockDebuginfodClient, mockBucket *mockobjstore.MockBucket) {},
 			validate: func(t *testing.T, p *googlev1.Profile) {
-				require.False(t, p.Mapping[0].HasFunctions)
+				require.True(t, p.Mapping[0].HasFunctions)
+				require.Len(t, p.Location[0].Line, 1)
+				require.Len(t, p.Location[1].Line, 1)
+
+				fn1 := p.StringTable[p.Function[p.Location[0].Line[0].FunctionId-1].Name]
+				fn2 := p.StringTable[p.Function[p.Location[1].Line[0].FunctionId-1].Name]
+				require.Contains(t, fn1, "linux-vdso.1.so")
+				require.Contains(t, fn1, "0xa4c")
+				require.Contains(t, fn2, "linux-vdso.1.so")
+				require.Contains(t, fn2, "0x9f0")
 			},
 		},
 		{